Triceps denervation as a predictor of elbow flexion contractures in C5 and C6 tetraplegia

Neuromuscular consequences of spinal cord injury: New mechanistic insights and clinical considerations

The spinal cord facilitates communication between the brain and the body, containing intrinsic systems that work with lower motor neurons (LMNs) to manage movement. Spinal cord injuries (SCIs) can lead to partial paralysis and dysfunctions in muscles below the injury. While traditionally this paralysis has been attributed to disruptions in the corticospinal tract, a growing body of work demonstrates LMN damage is a factor. Motor units, comprising the LMN and the muscle fibers with which they connect, are essential for voluntary movement. Our understanding of their changes post-SCI is still emerging, but the health of motor units is vital, especially when considering innovative SCI treatments like nerve transfer surgery. This review seeks to collate current literature on how SCI impact motor units and explore neuromuscular clinical implications and treatment avenues. SCI reduced motor unit number estimates, and surviving motor units had impaired signal transmission at the neuromuscular junction, force-generating capacity, and excitability, which have the potential to recover chronically, yet the underlaying mechanisms are unclear. Furthermore, electrodiagnostic evaluations can aid in assessing the health lower and upper motor neurons, identify suitable targets for nerve transfer surgeries, and detect patients with time sensitive injuries. Lastly, many electrodiagnostic abnormalities occur in both chronic and acute SCI, yet factors contributing to these abnormalities are unknown. Future studies are required to determine how motor units adapt following SCI and the clinical implications of these adaptations.

Motor unit activity and synaptic inputs to motoneurons in the caudal part of the injured spinal cord

Spinal cord injury (SCI) disrupts neuronal function below the lesion epicenter, causing disuse muscle atrophy. We investigated motor unit (MU) activity and synaptic inputs to motoneurons in the caudal region of the injured spinal cord. Participants with C4-C7 cervical injuries were studied. The extensor digitorum communis (EDC) muscle, which is mainly innervated by C8, was assessed for disuse muscle atrophy. Using advanced electromyography and signal-processing techniques, we examined the concurrent activation of a substantial population of MUs during force-tracking tasks. We found that in participants with SCI (n = 9), both MU discharge rates and the amplitudes of MU action potentials were significantly lower than in controls (n = 9). After SCI, MUs were recruited in a limited force range as the strength of muscle contractions increased, implying a disruption in the orderly MU recruitment pattern. Coherence analysis revealed reduced synaptic inputs to motoneurons in the delta band (0.5-5 Hz) for participants with SCI, suggesting diminished common synaptic inputs to the EDC muscle. In addition, participants with SCI exhibited greater muscle force variability. Using principal component analysis on low-frequency MU discharge rates, we found that the first common component (FCC) captured the most discharge variability in participants with SCI. The coefficients of variation (CV) of the FCC correlated with force signal CVs, suggesting force variability mainly results from common synaptic inputs to the EDC muscle after SCI. These results advance our understanding of the neurophysiology of disuse muscle atrophy in human SCI, paving the way for therapeutic interventions to restore muscle function.NEW & NOTEWORTHY This study analyzed motor unit (MU) function below the lesion epicenter in patients with spinal cord injury (SCI). We found reduced MU discharge rates and action potential amplitudes in participants with SCI compared with controls. The strength of common synaptic inputs to motoneurons was reduced in patients with SCI, with increased force variability primarily due to low-frequency oscillations of common inputs. This study enhances understanding of neurophysiological and behavioral changes in disuse muscle atrophy post-SCI.

Functional passive range of motion of individuals with chronic cervical spinal cord injury

OBJECTIVE

Functional passive range of motion (PROM) requirements for individuals with cervical spinal cord injury (SCI) are clinically accepted despite limited evidence defining the specific PROM needed to perform functional tasks. The objective of this investigation was to better define the minimum PROM needed for individuals with cervical SCI to achieve optimal functional ability, and as a secondary outcome gather self-reported standardized functional data via the Spinal Cord Independence Measure-III (SCIM-III), and the Spinal Cord Injury Functional Index (SCI-FI).

DESIGN

Observational cohort.

SETTING

128-bed rehabilitation hospital with inpatient and outpatient spinal cord injury rehabilitation programs.

PARTICIPANTS

A convenience sample of 29 community-dwelling individuals with chronic (greater than one year) tetraplegic SCI (C5-8) who use a wheelchair for mobility.

INTERVENTIONS

None.

OUTCOME MEASURES

Therapist goniometric measurement of upper and lower extremity PROM, and participant completion of a demographic questionnaire and two functional self-report measures (SCIM-III and SCI-FI) were completed.

RESULTS

Compared to the general population, differences observed in our study participants included limitations in forearm pronation and elbow extension and increased shoulder extension and wrist extension (likely related to prop sitting). Elbow hyperextension was noted in one-third of the participants. Limitations in straight leg raise, hip flexion, abduction, and internal rotation, in combination with increased hip external rotation suggested these individuals with cervical SCI potentially completed activities of daily living (ADLs) in frog-sitting, rather than long-sitting. Ankle plantarflexion contractures were found in many participants. Shoulder horizontal adduction, elbow extension, hip flexion, knee flexion, ankle plantarflexion, and forefoot eversion ROM were associated with functional performance.

CONCLUSION

Based on our results healthcare providers should work with individuals with cervical SCI to develop long term PROM plans to optimize functional abilities.

Motor Point Topography of Fundamental Grip Actuators in Tetraplegia: Implications in Nerve Transfer Surgery

The differentiation between an upper motoneuron (UMN) lesion and lower motoneuron (LMN) lesion of forearm muscles in patients with tetraplegia is critical for the choice of treatment strategy. Specifically, the M. pronator teres (PT), M. flexor digitorum profundus III (FDPIII), and M. flexor pollicis longus (FPL) were studied since they represent key targets in nerve transfer surgery to restore grasp function. Forearm muscles of 24 patients with tetraplegia were tested bilaterally with electrical stimulation (ES) to determine whether UMN or LMN lesion was present. For detecting and testing the nerve stimulation points, a standardized mapping was developed and clinically applied. The relationship between the anatomical segmental spinal innervation and the innervation pattern tested by ES was determined. The data of 44 arms were analyzed. For PT, 19 arms showed an intact UMN, 18 arms an UMN lesion, and seven arms partial denervation. For FDPIII, three arms demonstrated an intact UMN, 26 arms an UMN lesion, 10 arms partial denervation, and five arms denervation. For FPL, two arms presented an intact UMN, 16 arms an UMN lesion, 12 arms partial denervation, and 14 arms denervation. A total of 20.1% ES tested muscles were partially denervated. In four patients, only one arm could be tested because of surgery-related limitations. According to the level of lesion and the segmental spinal innervation, most denervated muscles were present in the patient group C6 to C8. The ES, together with the developed mapping system, is reliable and can be recommended for standardized testing in surgery and rehabilitation. It offers the possibility to detect if and to what extent UMN and LMN lesions are present for the target muscles. It allows for refined pre-operative diagnostics and prognostics in spinal cord injury neurotization surgery.

Advanced Assessment of the Upper Limb in Tetraplegia: A Three-Tiered Approach to Characterizing Paralysis

Background: More than half of all individuals who sustain a spinal cord injury (SCI) experience some degree of impairment in the upper limb. Functional use of the arm and hand is of paramount importance to these individuals. Fortunately, the number of clinical trials and advanced interventions targeting upper limb function are increasing, generating optimism for improved recovery and restoration after SCI. New interventions for restoring function and improving recovery require more detailed examination of the motor capacities of the upper limb. Objectives: The purpose of this article is to introduce a three-tiered approach to evaluating motor function, with specific attention to the characteristics of weak and fully paralyzed muscles during acute rehabilitation. The three tiers include (1) evaluation of voluntary strength via manual muscle testing, (2) evaluation of lower motor neuron integrity in upper motor neuron-paralyzed muscles using surface electrical stimulation, and (3) evaluation of latent motor responses in paralyzed muscles that exhibit a strong response to electrical stimulation, using surface electromyographic recording electrodes. These characteristics contribute important information that can be utilized to mitigate potential secondary conditions such as contractures and identify effective interventions such as activity-based interventions or reconstructive procedures. Our goal is to encourage frontline clinicians - occupational and physical therapists who are experts in muscle assessment - to consider a more in-depth analysis of paralysis after SCI. Conclusion: Given the rapid advancements in SCI research and clinical interventions, it is critical that methods of evaluation and classification evolve. The success or failure of these interventions may depend on the specific characteristics identified in our three-tiered assessment. Without this assessment, the physiological starting point for each individual is unknown, adding significant variability in the outcomes of these interventions.

Factors associated with upper extremity contractures after cervical spinal cord injury: A pilot study

OBJECTIVE

To examine the prevalence of joint contractures in the upper limb and association with voluntary strength, innervation status, functional status, and demographics in a convenience sample of individuals with cervical spinal cord injury to inform future prospective studies.

DESIGN

Cross-sectional convenience sampled pilot study.

SETTING

Department of Veterans Affairs Research Laboratory.

PARTICIPANTS

Thirty-eight participants with cervical level spinal cord injury.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Contractures were measured with goniometric passive range of motion. Every joint in the upper extremity was evaluated bilaterally. Muscle strength was measured with manual muscle testing. Innervation status was determined clinically with surface electrical stimulation. Functional independence was measured with the Spinal Cord Independence Measure III (SCIM-III).

RESULTS

Every participant tested had multiple joints with contractures and, on average, participants were unable to achieve the normative values of passive movement in 52% of the joints tested. Contractures were most common in the shoulder and hand. There was a weak negative relationship between percentage of contractures and time post-injury and a moderate positive relationship between percentage of contractures and age. There was a strong negative correlation between SCIM-III score and percentage of contractures.

CONCLUSIONS

Joint contractures were noted in over half of the joints tested. These joint contractures were associated with decreased functional ability as measured by the SCIM-III. This highlights the need the need for detailed evaluation of the arm and hand early after injury as well as continued monitoring of joint characteristics throughout the life course of the individual with tetraplegia.

EVALUATION OF MUSCLE STRENGTH IN MEDULLAR INJURY: A LITERATURE REVIEW

ABSTRACT Objective: To identify the tools used to evaluate muscle strength in subjects with spinal cord injury in both clinical practice and scientific research. Methods: Initially, the literature review was carried out to identify the tools used in scientific research. The search was conducted in the following databases: Virtual Health Library (VHL), Pedro, and PubMed. Studies published between 1990 and 2016 were considered and selected, depicting an evaluation of muscle strength as an endpoint or for characterization of the sample. Next, a survey was carried out with physiotherapists to identify the instruments used for evaluation in clinical practice, and the degree of satisfaction of professionals with respect to them. Results: 495 studies were found; 93 were included for qualitative evaluation. In the studies, we verified the use of manual muscle test with different graduation systems, isokinetic dynamometer, hand-held dynamometer, and manual dynamometer. In clinical practice, the manual muscle test using the motor score recommended by the American Spinal Cord Injury Association was the most used method, despite the limitations highlighted by the physiotherapists interviewed. Conclusion: In scientific research, there is great variation in the methods and tools used to evaluate muscle strength in individuals with spinal cord injury, differently from clinical practice. The tools available and currently used have important limitations, which were highlighted by the professionals interviewed. No instrument depicts direct relationship of muscle strength and functionality of the subject. There is no consensus as to the best method for assessing muscle strength in spinal cord injury, and new instruments are needed that are specific for use in this population.

Motoneuron Death after Human Spinal Cord Injury

The severe muscle weakness and atrophy measured after human spinal cord injury (SCI) may relate to chronic muscle denervation due to motoneuron death and/or altered muscle use. The aim of this study was to estimate motoneuron death after traumatic human SCI. The diameter and number of myelinated axons were measured in ventral roots post-mortem because ventral roots contain large diameter (> 7 μm) myelinated axons that typically arise from motoneurons and innervate skeletal muscle. In four cases (SCI levels C7, C8, T4, and L1) involving contusion (n = 3) or laceration (n = 1), there was a significant reduction in the number of large diameter myelinated axons at the lesion epicenter (mean ± standard error [SE]: 45 ± 11% Uninjured), one level above (51 ± 14%), and one (27 ± 12%), two (45 ± 40%), and three (54 ± 23%) levels below the epicenter. Reductions in motoneuron numbers varied by side and case. These deficits result from motoneuron death because the gray matter was destroyed at and near the lesion epicenter. Muscle denervation must ensue. In seven cases, ventral roots at or below the epicenter had large diameter myelinated axons with unusually thin myelin, a sign of incomplete remyelination. The mean ± SE g ratio (axon diameter/fiber diameter) was 0.60 ± 0.01 for axons of all diameters in five above-lesion ventral roots, but increased significantly for large diameter fibers (≥ 12 μm) in three roots at the lesion epicenter. Motoneuron death after human SCI will coarsen muscle force gradation and control, while extensive muscle denervation will stifle activity-based treatments.

Age at spinal cord injury determines muscle strength

As individuals with spinal cord injury (SCI) age they report noticeable deficits in muscle strength, endurance and functional capacity when performing everyday tasks. These changes begin at ~45 years. Here we present a cross-sectional analysis of paralyzed thenar muscle and motor unit contractile properties in two datasets obtained from different subjects who sustained a cervical SCI at different ages (≤46 years) in relation to data from uninjured age-matched individuals. First, completely paralyzed thenar muscles were weaker when C6 SCI occurred at an older age. Muscles were also significantly weaker if the injury was closer to the thenar motor pools (C6 vs. C4). More muscles were strong (>50% uninjured) in those injured at a younger (≤25 years) vs. young age (>25 years), irrespective of SCI level. There was a reduction in motor unit numbers in all muscles tested. In each C6 SCI, only ~30 units survived vs. 144 units in uninjured subjects. Since intact axons only sprout 4-6 fold, the limits for muscle reinnervation have largely been met in these young individuals. Thus, any further reduction in motor unit numbers with time after these injuries will likely result in chronic denervation, and may explain the late-onset muscle weakness routinely described by people with SCI. In a second dataset, paralyzed thenar motor units were more fatigable than uninjured units. This gap widened with age and will reduce functional reserve. Force declines were not due to electromyographic decrements in either group so the site of failure was beyond excitation of the muscle membrane. Together, these results suggest that age at SCI is an important determinant of long-term muscle strength, and fatigability, both of which influence functional capacity.

Human spinal cord injury: motor unit properties and behaviour

Spinal cord injury (SCI) results in widespread variation in muscle function. Review of motor unit data shows that changes in the amount and balance of excitatory and inhibitory inputs after SCI alter management of motoneurons. Not only are units recruited up to higher than usual relative forces when SCI leaves few units under voluntary control, the force contribution from recruitment increases due to elevation of twitch/tetanic force ratios. Force gradation and precision are also coarser with reduced unit numbers. Maximal unit firing rates are low in hand muscles, limiting voluntary strength, but are low, normal or high in limb muscles. Unit firing rates during spasms can exceed voluntary rates, emphasizing that deficits in descending drive limit force production. SCI also changes muscle properties. Motor unit weakness and fatigability seem universal across muscles and species, increasing the muscle weakness that arises from paralysis of units, motoneuron death and sensory impairment. Motor axon conduction velocity decreases after human SCI. Muscle contractile speed is also reduced, which lowers the stimulation frequencies needed to grade force when paralysed muscles are activated with patterned electrical stimulation. This slowing does not necessarily occur in hind limb muscles after cord transection in cats and rats. The nature, duration and level of SCI underlie some of these species differences, as do variations in muscle function, daily usage, tract control and fibre-type composition. Exploring this diversity is important to promote recovery of the hand, bowel, bladder and locomotor function most wanted by people with SCI.

Triceps Brachii in Incomplete Tetraplegia: EMG and Dynamometer Evaluation of Residual Motor Resources and Capacity for Strengthening

BACKGROUND

Candidates for activity-based therapy after spinal cord injury (SCI) are often selected on the basis of manual muscle test scores and the classification of the injury as complete or incomplete. However, these scores may not adequately predict which individuals have sufficient residual motor resources for the therapy to be beneficial.

OBJECTIVE

We performed a preliminary study to see whether dynamometry and quantitative electromyography (EMG) can provide a more detailed assessment of residual motor resources.

METHODS

We measured elbow extension strength using a hand-held dynamometer and recorded fine-wire EMG from the triceps brachii muscles of 4 individuals with C5, C6, or C7 level SCI and 2 able-bodied controls. We used EMG decomposition to measure motor unit action potential (MUAP) amplitudes and motor unit (MU) recruitment and firing-rate profiles during constant and ramp contractions.

RESULTS

All 4 subjects with cervical SCI (cSCI) had increased MUAP amplitudes indicative of denervation. Two of the subjects with cSCI had very weak elbow extension strength (<4 kg), dramatically reduced recruitment, and excessive firing rates (>40 pps), suggesting profound loss of motoneurons. The other 2 subjects with cSCI had stronger elbow extension (>6 kg), more normal recruitment, and more normal firing rates, suggesting a substantial remaining motoneuron population.

CONCLUSIONS

Dynamometry and quantitative EMG may provide information about the extent of gray matter loss in cSCI to help guide rehabilitation strategies.

Dynamic motor compensations with permanent, focal loss of forelimb force after cervical spinal cord injury

Incomplete cervical lesion is the most common type of human spinal cord injury (SCI) and causes permanent paresis of arm muscles, a phenomenon still incompletely understood in physiopathological and neuroanatomical terms. We performed spinal cord hemisection in adult rats at the caudal part of the segment C6, just rostral to the bulk of triceps brachii motoneurons, and analyzed the forces and kinematics of locomotion up to 4 months postlesion to determine the nature of motor function loss and recovery. A dramatic (50%), immediate and permanent loss of extensor force occurred in the forelimb but not in the hind limb of the injured side, accompanied by elbow and wrist kinematic impairments and early adaptations of whole-body movements that initially compensated the balance but changed continuously over the follow-up period to allow effective locomotion. Overuse of both contralateral legs and ipsilateral hind leg was evidenced since 5 days postlesion. Ipsilateral foreleg deficits resulted mainly from interruption of axons that innervate the spinal cord segments caudal to the lesion, because chronic loss (about 35%) of synapses was detected at C7 while only 14% of triceps braquii motoneurons died, as assessed by synaptophysin immunohistochemistry and retrograde neural tracing, respectively. We also found a large pool of propriospinal neurons projecting from C2-C5 to C7 in normal rats, with topographical features similar to the propriospinal premotoneuronal system of cats and primates. Thus, concurrent axotomy at C6 of brain descending axons and cervical propriospinal axons likely hampered spontaneous recovery of the focal neurological impairments.

Surgical restoration of arm and hand function in people with tetraplegia

Improved hand and arm function is the most sought after function for people living with a cervical spinal cord injury (SCI). Surgical techniques have been established to increase upper extremity function for tetraplegics, focusing on restoring elbow extension, wrist movement, and hand opening and closing. Additionally, more innovative treatments that have been developed (implanted neuroprostheses and nerve transfers) provide more options for improving function and quality of life. One of the most important steps in the process of restoring upper extremity function in people with tetraplegia is identifying appropriate candidates - typically those with American Spinal Injury Association (ASIA) motor level C5 or greater. Secondary complications of SCI can pose barriers to restoring function, particularly upper extremity spasticity. A novel approach to managing spasticity through high-frequency alternating currents designed to block unwanted spasticity is being researched at the Cleveland FES Center and may improve the impact of reconstructive surgery for these individuals. The impact of these surgeries is best measured within the framework of the World Health Organization's International Classification of Function, Disability and Health. Outcome measures should be chosen to reflect changes within the domains of body functions and structures, activity, and participation. There is a need to strengthen the evidence in the area of reconstructive procedures for people with tetraplegia. Research continues to advance, providing more options for improved function in this population than ever before. The contribution of well-designed outcome studies to this evidence base will ultimately help to address the complications surrounding access to the procedures.

A synthesis of best evidence for the restoration of upper-extremity function in people with tetraplegia

PURPOSE

Because upper-limb function represents overall function for individuals with tetraplegia, the restoration of upper-extremity function is exceedingly important for this population. The purpose of this review was to identify interventions that optimize upper-limb function after tetraplegia based on best available evidence.

METHODS

A search of MEDLINE, AMED, and PubMed with the search terms "hand function AND tetraplegia" and "upper limb function AND tetraplegia" found 384 articles. After elimination of duplicates and review of titles and abstracts, 43 studies were found to be applicable. Study quality of all applicable studies was assessed with a modified version of the Scottish Intercollegiate Guidelines Network for Cohort Studies methodology.

RESULTS

The applicable studies were organized into three categories: conventional therapies (CT), electrical stimulation therapies (ES), and surgical interventions (SI). The proportion of papers in each category that presented with sufficient methodological quality to contribute to best evidence was as follows: CT: 0/2; ES: 10/21; SI: 6/20.

CONCLUSIONS

ES therapies are beneficial as assistive technologies and as therapeutic intervention in the subacute phase of recovery. SIs are suitable for individuals who meet very specific criteria for tendon-transfer surgery. Further clinical trials are warranted for ES and SI therapies to substantiate prescription of therapeutics.

Do additional inputs change maximal voluntary motor unit firing rates after spinal cord injury?

BACKGROUND

Motor unit firing frequencies are low during maximal voluntary contractions (MVCs) of human thenar muscles impaired by cervical spinal cord injury (SCI).

OBJECTIVE

This study aimed to examine whether thenar motor unit firing frequencies increase when driven by both maximal voluntary drive and other concurrent inputs compared with an MVC alone.

METHODS

Motor unit firing rates, force, and surface electromyographic activity (EMG) were compared across 2 contractions: (a) MVC alone and (b) MVC combined with another input (combination contraction). Other inputs (conditions) included vibration, heat, or cold applied to the anterior surface of the forearm, electrical stimulation delivered to the anterior surface of the middle finger, a muscle spasm, or a voluntary contraction of the contralateral thenar muscles against resistance.

RESULTS

The maximal firing frequency (n = 68 units), force, and electromyographic activity (n = 92 contraction pairs) were all significantly higher during the combined contractions compared with MVCs alone. There was a 3-way interaction between contraction, condition, and subject for maximal motor unit firing rates, force, and EMG. Thus, combined contraction responses were different for conditions across subjects. Some conditions (eg, a muscle spasm) resulted in more effective and more frequent responses (increases in unit firing frequency, force, EMG in >50% contractions) than others. Recruitment of new units also occurred in combined contractions.

CONCLUSIONS

Motoneurons are still responsive to additional afferent inputs from various sources when rate modulation from voluntary drive is limited by SCI. Individuals with SCI may be able to combine inputs to control functional tasks they cannot perform with voluntary drive alone.

Dynamic splinting for pronation contracture following a spinal cord injury

Background

This report discusses the success of using multiple protocols/modalities to reduce forearm contracture in a 34-year-old, African American man who had suffered a spinal cord injury (SCI) over 2 years before this treatment. The patient's initial maximal active range of motion (AROM) in supination was −85° left and −60° right, and his initial passive range of motion (PROM) was +12° left and +50° right.

Methods

Intervention included occupational therapy five times per week and the protocols employed included manual AROM and PROM training, isometric strength training, handwriting, self-feeding and grooming training. Electrical stimulation for shoulder flexion and elbow extension, and a unique new modality, the Supination Dynasplint®, was also used for 45 min on each arm, twice daily.

Results

After three months, the patient regained over 40° AROM of supination in each arm. This benefitted the patient's ability to use utensils for eating, improved his handwriting skills and he regained the ability to use a urinal at night while in bed.

Involuntary, electrically excitable nerve transfer for denervation: results from an animal model

PURPOSE

The purpose of this study was to evaluate the efficacy of "paralyzed" nerve transfer (ie, transfer of an involuntary, nondegenerated, electrically excitable nerve onto an involuntary, degenerated, non-electrically excitable nerve) and functional electrical stimulation for reinnervation. We hypothesized that lower motor neuron cell body continuity with the motor cortex, via intact upper motor neurons, is not necessary for reinnervation of the extremities.

METHODS

Fischer 344 rats had lower thoracic spinal cord injury (SCI) followed by unilateral tibial nerve transection and delayed peroneal ("paralyzed") to tibial nerve transfer (group A) or primary neurorrhaphy (group B). Control groups had SCI and a unilateral hindlimb incision and nerve exposure only (group C) or a unilateral hindlimb disection and transection of both the tibial and peroneal nerves (group D). Three months after surgery, the proximal peroneal (group A) or proximal tibial (groups B, C, and D) nerves were electrically stimulated in vivo, and gastrocnemius force production was measured on both the operative and nonoperative hindlimbs. In addition, the distal tibial nerves from both the experimental and control-side hindlimbs were sectioned and stained with anti-neurofilament protein to determine total axon counts.

RESULTS

Mean gastrocnemius force return and mean axonal regeneration was 47% and 51%, respectively, for group A animals (n = 9), 68% and 73% for group B animals (n = 4), 97% and 99% for group C animals (n = 4), and 0 and 2% for group D animals (n = 4). A 1-way analysis of variance for independent samples yielded significant differences between groups A, B, and C for gastrocnemius force return and between all groups for axonal regeneration.

CONCLUSIONS

Paralyzed nerve transfer produces a mean of approximately 50% return of gastrocnemius force and axonal regeneration. Paralyzed nerve transfer combined with functional electrical stimulation is a viable method for reanimating denervated motor units in the setting of SCI.

Measurement issues related to upper limb interventions in persons who have tetraplegia

Measurement of upper limb function in persons with tetraplegia poses significant issues for clinicians and researchers. It is crucial that measures detect the small but significant improvements in hand function that may or may not occur as a result of our interventions. Before determining how we measure changes from upper limb interventions, we must establish what outcomes are of greatest interest, and for whom. Many issues have an impact on both the measurement and interpretative process.

The epidemiology of major joint contractures: a systematic review of the literature

Current knowledge on the epidemiology of major joint contractures is limited. We systematically reviewed the literature to identify studies examining the epidemiology of joint contracture regardless of clinical condition. Epidemiologic measures of interest were prevalence, incidence, and prognostic risk factors. We used Medline to identify all epidemiologic studies of major joint contractures published from 1966 to March 2005. There was a high prevalence of major joint contractures. Most studies focused on one joint rather than including all relevant major contractures. However, most studies did provide a definition of a contracture or the measures used to assess contractures. Immobility is a highly prevalent disability in at-risk populations, and constitutes a tremendous burden to patients in nursing homes, hospitals, and the outpatient community. The lack of epidemiologic data is a major impediment to providing appropriate treatment.

Fatigue of muscles weakened by death of motoneurons

Weakness is a characteristic of muscles influenced by the postpolio syndrome (PPS), amyotrophic lateral sclerosis (ALS), and spinal cord injury (SCI). The strength deficits relate to changes in muscle use and to the chronic denervation that can follow the spinal motoneuron death common to these disorders. PPS, ALS, and SCI also involve variable amounts of supraspinal neuron death, the effects of which on muscle weakness remains unclear. Nevertheless, weakness of muscle itself defines the functional consequences of these disorders. A weaker muscle requires an individual to work that muscle at higher than usual intensities relative to its maximal capacity, inducing progressive fatigue and an increased sense of effort. Little evidence is available to suggest that the fatigue commonly experienced by individuals with these disorders relates to an increase in the intrinsic fatigability of the muscle fibers. The only exception is when SCI induces chronic muscle paralysis. To reduce long-term functional deficits in these disorders, studies must identify the signaling pathways that influence neuron survival and determine the factors that encourage and limit sprouting of motor axons. This may ensure that a greater proportion of the fibers in each muscle remain innervated and available for use.

Physical capacity in wheelchair-dependent persons with a spinal cord injury: a critical review of the literature

STUDY DESIGN

Review of publications.

OBJECTIVE

To assess the level of physical capacity (peak oxygen uptake, peak power output, muscle strength of the upper extremity and respiratory function) in wheelchair-dependent persons with a spinal cord injury (SCI).

SETTING

Erasmus MC, University Medical Centre Rotterdam, The Netherlands.

METHODS

Pubmed (Medline) search of publications from 1980 onwards. Studies were systematically assessed. Weighted means were calculated for baseline values.

RESULTS

In tetraplegia, the weighted mean for peak oxygen uptake was 0.89 l/min for the wheelchair exercise test (WCE) and 0.87 l/min for arm-cranking or hand-cycling (ACE). The peak power output was 26 W (WCE) and 40 W (ACE). In paraplegia, the peak oxygen uptake was 2.10 l/min (WCE) and 1.51 l/min (ACE), whereas the peak power output was 74 W (ACE) and 85 W (WCE). In paraplegia, muscle strength of the upper extremity and respiratory function were comparable to that in the able-bodied population. In tetraplegia muscle strength varied greatly, and respiratory function was reduced to 55-59% of the predicted values for an age-, gender- and height-matched able-bodied population.

CONCLUSIONS

Physical capacity is reduced and varies in SCI. The variation between results is caused by population and methodological differences. Standardized measurement of physical capacity is needed to further develop comparative values for clinical practice and rehabilitation research.

Twelve weeks of nightly stretch does not reduce thumb web-space contractures in people with a neurological condition: a randomised controlled trial

QUESTION

What is the effectiveness of 12 weeks of nightly stretch in reducing thumb web-space contracture in people with neurological conditions?

DESIGN

Assessor-blinded, randomised controlled trial.

PARTICIPANTS

Forty-four (one dropout)community-dwelling patients with a neurological condition (14 stroke, 7 traumatic brain injury, 23 spinal cord injury) who had uni or bilateral thumb web-space contractures (60 thumbs).

INTERVENTION

The experimental thumbs were splinted into a stretched,abducted position each night for 12 weeks. The control thumbs were not splinted.

OUTCOME MEASURES

Thumb web-space was measured as the carpometacarpal angle during the application of a 0.9 Nm abduction torque before and after intervention.

RESULTS

The mean increase in thumb web-space after 12 weeks was 1 deg (95% CI, -1 to 2).

CONCLUSION

Intensive stretch administered regularly over three months does not reduce thumb web-space contractures in neurological conditions.